Artificial intelligence applied to the automatic analysis of absorption spectra. Objective measurement of the fine structure constant

TL;DR

This paper introduces an automated AI-based method combining genetic algorithms, non-linear least squares, and Bayesian Model Averaging to analyze high-resolution absorption spectra for measuring the fine structure constant, improving objectivity and reproducibility.

Contribution

It presents a novel unified automated approach that outperforms human analysis in measuring the fine structure constant from spectra, reducing systematic uncertainties.

Findings

Automated method yields consistent results with no variation in alpha.

The approach is robust against model choice uncertainties.

Method outperforms traditional human analysis in accuracy and efficiency.

Abstract

A new and automated method is presented for the analysis of high-resolution absorption spectra. Three established numerical methods are unified into one "artificial intelligence" process: a genetic algorithm (GVPFIT); non-linear least-squares with parameter constraints (VPFIT); and Bayesian Model Averaging (BMA). The method has broad application but here we apply it specifically to the problem of measuring the fine structure constant at high redshift. For this we need objectivity and reproducibility. GVPFIT is also motivated by the importance of obtaining a large statistical sample of measurements of $\Delta\alpha/\alpha$. Interactive analyses are both time consuming and complex and automation makes obtaining a large sample feasible. In contrast to previous methodologies, we use BMA to derive results using a large set of models and show that this procedure is more robust than a human picking a single preferred model since BMA avoids the systematic uncertainties associated with model choice. Numerical simulations provide stringent tests of the whole process and we show using both real and simulated spectra that the unified automated fitting procedure out-performs a human interactive analysis. The method should be invaluable in the context of future instrumentation like ESPRESSO on the VLT and indeed future ELTs. We apply the method to the $z_{abs} = 1.8389$ absorber towards the $z_{em} = 2.145$ quasar J110325-264515. The derived constraint of $\Delta\alpha/\alpha = 3.3 \pm 2.9 \times 10^{-6}$ is consistent with no variation and also consistent with the tentative spatial variation reported in Webb et al (2011) and King et al (2012).